Highly reactive zerovalent metals are desirable reagents for the synthesis of new organic and organometallic compounds. They can be used in the synthesis of many drugs, agrochemicals, monomers for use in polymers, highly conducting polymers, dyes, synthetics fibers, fluorocarbons, and a long list of other specialty chemicals. They can also be used in the preparation of novel information storage devices, nonlinear optical materials, and novel batteries. They are particularly useful in the reactions of organic and inorganic substrates, either in a catalytic fashion or with the consumption of the metal.
There have been numerous approaches used to increase the reactivity of zerovalent metals. This is desirable in order to carry out known reactions under relatively mild conditions, to improve yields, and to increase the reactivity of less reactive substrates. For example, in the direct synthesis of Grignard reagents (organomagnesium reagents) from the reaction of magnesium metal and an organic halide, higher reaction temperatures and more strongly coordinating solvents have been used to improve yields. Also, methods have been developed to activate the magnesium metal using iodine or catalytic amounts of ethylene bromide or ethyl bromide. In the synthesis of organozinc compounds from the oxidative addition of zinc metal to alkyl iodides, several methods have been used to activate zinc towards oxidative addition reactions. These include washing the zinc metal with HCl solution, using a Zn--Cu couple, and metal-solvent cocondensation, for example. In spite of these methods, the direct oxidative addition of zinc metal to organic halides has been limited to relatively reactive halides such as alkyl iodides or .alpha.-haloesters. Most alkyl bromides, alkyl chlorides, vinyl halides, and aryl halides do not directly react with zinc metal.
Other approaches used to generate highly reactive zerovalent metals include-metal atom vapor techniques, ultrasound techniques, and the reduction of metal halide salts. The zerovalent metal species produced from the reduction of metal halide salts are typically more reactive and better synthetic tools than are commercial metals or metals produced from standard activating techniques. The properties of the zerovalent metals produced are, however, generally dependent upon the solvent used, the reducing agent, and the halide anion of the metal salt being reduced. For example, magnesium metal in the form of a black powder can be obtained by reducing magnesium halide salts in an ethereal solvent with molten sodium or potassium. However, the use of an alkali metal in conjunction with an electron carrier such as naphthalene can produce magnesium powder of different reactivity. Furthermore, MgCl.sub.2 typically produces a more reactive zerovalent metal than does MgF.sub.2.
There is a continuing need for highly reactive zerovalent metals that can be utilized in a broad spectrum of syntheses of various chemical compounds. An object of the invention is to produce zerovalent metal species that are more reactive, or possess different reactivity, than those obtained from traditional methods. Another object of the invention is to produce zerovalent metal species that are highly reactive towards oxidative addition. Yet another object of the invention is the direct production of a wide variety of organometallic compounds, e.g., aryl, heterocyclic, arylalkyl, and polymeric metal reagents that can undergo a number of valuable synthetic reactions. Still another object of the invention is to produce a wide variety of organometallic reagents that contain a broad spectrum of functional groups such as esters, ketones, nitriles, halides, amides, carbamates, epoxides, aldehydes, .alpha.,.beta.-unsaturated enones (e.g., esters and ketones), sulfoxides, sulfones, etc.